Oxygen separation module and apparatus

ABSTRACT

A module and an apparatus incorporating such module utilizing a plurality of tubular membrane elements, each configured to separate oxygen from an oxygen containing feed stream when an electric potential difference is applied to induce oxygen ion transport in an electrolyte thereof. The tubular membrane elements can be arranged in a bundle that is held in place by end insulating members. The insulating members can be positioned within opposed openings of end walls of a heated enclosure and can incorporate bores to allow an oxygen containing feed stream to flow past exposed ends of the tubular membrane elements for cooling the end seals of such elements. Further, first and second manifolds can be provided in a module in accordance with the present invention to collect separated oxygen from two separate portions of the tubular membrane elements.

FIELD OF THE INVENTION

The present invention relates to an oxygen separation module andapparatus that incorporates a plurality of tubular membrane elements,each configured to separate oxygen from an oxygen containing feed streamwhen an electric potential difference is applied to produce oxygen iontransport through an electrolyte of the tubular membrane elements. Moreparticularly, the present invention relates to such an oxygen separationmodule and apparatus in which manifolds to collect the separated oxygenare positioned at opposite ends of the tubular membrane elements and areconnected to the tubular membrane elements such that a portion of thetubular membrane elements are connected to one of the manifolds andanother portion of the tubular membrane elements are connected to theother of the manifolds.

BACKGROUND OF THE INVENTION

Electrically driven oxygen separators are used to separate oxygen fromoxygen containing feed, for example, air. Additionally, such devices arealso used in purification application where it is desired to purify anoxygen containing feed by separating oxygen from the feed. The devicecan also be configured to separate H2O into H2 and O2 or CO2 into CO andO2. Electrically driven oxygen separators can utilize tubular membraneelements having a layered structure containing an electrolyte layercapable of transporting oxygen ions when subjected to an elevatedtemperature, cathode and anode electrode layers located at oppositesurfaces of the electrolyte layer and current collector layers to supplyan electrical current to the cathode and anode electrode layers.

When the tubular membrane elements are subjected to the elevatedtemperature, the oxygen contained in a feed will ionize on one surfaceof the electrolyte layer, adjacent the cathode electrode layer bygaining electrons from an applied electrical potential. Under theimpetus of the applied electrical potential, the resulting oxygen ionswill be transported through the electrolyte layer to the opposite side,adjacent the anode layer and recombine into elemental oxygen.

The tubular membrane elements are housed in an electrically heatedcontainment to heat the tubular membrane elements to an operationaltemperature at which oxygen ions will be transported. Additionally, suchtubular membrane elements can be manifolded together such that theoxygen containing feed is passed into the heated containment and theseparated oxygen is withdrawn from the tubular membrane elements througha manifold. In certain purification applications, the oxygen containingfeed can be passed through the interior of the tubular membrane elementsand the separated oxygen can be withdrawn from the containment.

Typical materials that are used to form the electrolyte layer areyttrium or scandium stabilized zirconia and gadolinium doped ceria. Theelectrode layers can be made of mixtures of the electrolyte material anda conductive metal, a metal alloy or an electrically conductiveperovskite. Current collectors in the art have been formed of conductivemetals and metal alloys, such as silver as well as mixtures of suchmetals and metallic oxides.

The tubular membrane elements can be contained in one or more modules inwhich in each module, the tubular membrane elements are arranged inbundles and are held in place by end insulation members adjacent to theopposite ends of the tubular membrane elements. These modules can bepositioned within insulated, heated enclosures to heat the tubularmembrane elements to an operational temperature at which oxygen iontransport can occur. The insulated enclosure also has inlets and outletswithin end walls of the enclosure to allow an oxygen containing feedstream to be passed into the enclosure and thereby to contact thetubular membrane elements. As a result of the oxygen separation, aretentate stream is formed that is discharged from the enclosure throughthe outlet. This type of electrically driven oxygen separation device isshown in U.S. Patent Appln. Ser. No. 2010/076280 A1.

As can be appreciated, it is important that electrically driven oxygenseparation devices reliably deliver the oxygen and at the lowest costpossible. With respect to reliability, a major problem with electricallydriven oxygen separation devices, is that failure of the tubularmembrane elements can occur. As a result, the oxygen containing feedstream will pass through the point of failure in a particular tubularmembrane and little if any oxygen will be separated by the membrane thathas the defect. Since, a major advantage of supplying oxygen from anelectrically driven oxygen separation device is that the oxygen can beproduced at ultra-high purity, the defective tubular membrane elementwill result in an unacceptable decrease in purity of the oxygen product.Therefore, as a result of such failure, the electrically driven oxygenseparation device will have to be removed from service. Furthermore,such a device is most useful if the outlet of oxygen separation modulesare connected to a storage tank and the oxygen is stored at pressure. Inthe case of a tube failure, the stored oxygen in the tank will dischargethrough the fractured ceramic tube. In order to reduce costs, theelectrically driven oxygen separator has to be assembled in a costefficient manner. In the patent application discussed above, the use ofmodules of such elements coupled with polymeric end seals go a long waytoward reducing assembly costs. However, such ends seals representanother possible point of failure because they have only a limitedability to withstand the high temperatures that are necessary to inducethe oxygen ion transport in the tubular membrane elements.

As will be discussed, the present invention provides a module and anelectrically driven oxygen separation device that, among otheradvantages is capable of operating upon failure of one or more tubularmembrane elements and that is specifically designed to cool the endseals.

SUMMARY OF THE INVENTION

The present invention provides, in one aspect, a module for anelectrically driven oxygen separator that incorporates a plurality oftubular membrane elements. Each of the tubular membrane elements isconfigured to separate oxygen from an oxygen containing feed stream whenan electric potential difference is applied to induce oxygen iontransport in an electrolyte thereof A first manifold and a secondmanifold, configured to collect the oxygen, are spaced apart from oneanother with the tubular membrane elements situated between the firstmanifold and the second manifold. The first and second manifold areconnected to the tubular membrane elements such that oxygen is receivedby the first manifold from a first portion of the tubular membraneelements and by the second manifold from a second portion of the tubularmembrane elements.

Therefore, upon failure of at least one of the tubular membrane elementsin either the first portion or the second portion of the tubularmembrane elements, oxygen is able to be collected from either the firstportion or the second portion of the tubular membrane elements that donot include the at least one of the tubular membrane elements that hasfailed. Check valves can be provided to pneumatically isolate the failedtube and associated first or second tubular membrane elements. While theoxygen will of course be delivered at a lower rate after such a failure,unlike electrically driven oxygen separators of the prior art, thefailure of one or more elements will not necessarily result in theelectrically driven oxygen separator being withdrawn from service.

End seals can be located at opposite ends of the tubular membraneelements. Each of the first manifold and the second manifold have acollection element to collect the oxygen produced by the tubularelements and first and second elongated elements connected at one end tothe collection element and at the other end penetrating the end seals atthe opposite ends of the tubular membrane elements. The first of theelongated elements are of tubular configuration to conduct the oxygenand the second of the elongated elements are configured to prevent flowof the oxygen to the collection element of each of the first manifoldand the second manifold. The first of the elongated elements alternatingwith the second of the elongated elements such that as between twoadjacent tubular membrane elements, the oxygen flows from one of the twoadjacent tubular membrane elements to the collection element of thefirst manifold and from the other of the two adjacent tubular membraneelements to the collection element of the second manifold. The second ofthe elongated elements can be of solid configuration.

The end seals can comprise plug-like members located within the tubularmembrane element and formed by an elastomer to produce hermetic seals atthe opposite ends of the tubular membrane elements and deposits of aceramic adhesive located within the tubular membrane elements adjacentto the plug-like members and positioned to prevent outward movement ofthe plug-like members. The tubular membrane elements can be arranged ina bundle and are held in place by two opposed end insulation memberslocated adjacent to the opposed ends of the tubular membrane elements.In such case, each of the first manifold and the second manifold has aspider-like configuration with the first and the second elongatedelements radiating from the collection element of each of the firstmanifold and the second manifold. Further, each of the two opposed endinsulation members has an inlet opening for passage of the oxygencontaining feed stream.

Each of the tubular membrane elements has an inner anode layer, an outercathode layer and an electrolyte layer located between the anode layerand the cathode layer to form the electrolyte. Two current collectorlayers are located adjacent to and in contact with the anode layer andthe cathode layer and situated on the inside and outside of the tubularmembrane element to allow the electrical potential to be applied by apower source. The tubular membrane elements can be connected in seriesand contain current distributors of helical configuration in contactwith one of the two current collector layers on the inside of thetubular membrane elements to conduct an electrical current applied byelectrical conductors passing through the feed throughs.

In another aspect, the present invention provides an electrically drivenoxygen separation apparatus. Such apparatus is provided with anenclosure having two inlet regions, a heated interior region locatedbetween the inlet regions and having opposed end walls positionedadjacent to the inlet regions, opposed openings defined in the endwalls, a sidewall connecting the end walls and heating elementspositioned to heat the heated interior region. An outlet extends fromthe heated interior region and through the sidewall. A plurality oftubular membrane elements are provided that are each configured toseparate oxygen from an oxygen containing feed stream when an electricpotential difference is applied to induce oxygen ion transport in anelectrolyte thereof. End seals are located at opposite ends of thetubular membrane elements.

The tubular membrane elements are arranged in a bundle and held in placeby two opposed end insulation members located adjacent to the opposedends of the tubular membrane elements. The bundle is positioned withinthe enclosure and with the end insulation members situated within theopenings of the end walls and the opposed ends of the tubular membraneelements and the end seals thereof projecting outwardly from the endinsulation members and into the two inlet regions. At least one manifoldis connected to the tubular membrane elements and configured to collectthe oxygen produced by the tubular membrane elements. Inlets are locatedwithin the two end insulation members for passage of two oxygencontaining feed streams from the inlet regions to the heated interiorregion and two blowers connected to the two inlet regions to circulatethe oxygen containing feed stream into the inlet region and past the endseals to cool the end seals and then, through the inlets, thereby tocontact the membrane elements inside the heated enclosure and todischarge a heated retentate from the heated enclosure that is formed byseparation of the oxygen from the oxygen containing feed stream. Thecooling of the end seals help to prevent failure of the electricallydriven oxygen separator in the first instance.

As set forth above, the at least one manifold can be a first manifoldand a second manifold spaced apart from one another with the tubularmembrane elements situated between the first manifold and the secondmanifold. The first manifold and the second manifold are connected tothe tubular membrane elements such that oxygen is received by the firstmanifold from a first portion of the tubular membrane elements and bythe second manifold from a second portion of the tubular membraneelements. Upon failure of at least one of the tubular membrane elementsin either the first portion or the second portion of the tubularmembrane elements, oxygen is able to be collected from either the firstportion or the second portion of the tubular membrane elements that donot include the at least one of the tubular membrane elements that hasfailed.

Each of the first manifold and the second manifold can be provided witha collection element to collect the oxygen produced by the tubularelements and first and second elongated elements connected at one end tothe collection element and at the other end penetrating the end seals atthe opposite ends of the tubular membrane elements. The first of theelongated elements are of tubular configuration to conduct the oxygenand the second of the elongated elements are configured to prevent flowof the oxygen to the collection element of each of the first manifoldand the second manifold. The first of the elongated elements alternatewith the second of the elongated elements such that as between twoadjacent tubular membrane elements, the oxygen flows from one of the twoadjacent tubular membrane elements to the collection element of thefirst manifold and from the other of the two adjacent tubular membraneelements to the collection element of the second manifold.

The end seals can comprise plug-like members located within the tubularmembrane element and formed by an elastomer to produce hermetic seals atthe opposite ends of the tubular membrane elements and deposits of aceramic adhesive located within the tubular membrane elements adjacentto the plug-like members and positioned to prevent outward movement ofthe plug-like members. As indicated above, the cooling of such end sealshas proven to be critical for preventing failure of the electricallydriven oxygen separation device. The second of the elongated elementscan be of solid configuration. Each of the first manifold and the secondmanifold has a spider-like configuration with the first and the secondelongated elements radiating from the collection element of each of thefirst manifold and the second manifold.

Each of the membrane elements has an inner anode layer, an outer cathodelayer and an electrolyte layer located between the anode layer and thecathode layer to form the electrolyte. Two current collector layers arelocated adjacent to and in contact with the anode layer and the cathodelayer and situated on the inside and outside of the tubular membraneelement to allow the electrical potential to be applied by a powersource. The tubular membrane elements can be connected in series and thetubular membrane elements can contain current distributors of helicalconfiguration in contact with one of the two current collector layers onthe inside of the tubular membrane elements to conduct an electricalcurrent applied by electrical conductors passing through the feedthroughs.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims that distinctly point outthe subject matter that Applicants regard as their invention, it isbelieved that the invention will be understood when taken in connectionwith the accompanying drawings in which:

FIG. 1 is a schematic sectional view of an electrically driven oxygenseparation apparatus of the present invention;

FIG. 2 is an elevational view of a module of the present invention;

FIG. 3 is an enlarged, fragmentary perspective view of the module shownin FIG. 2;

FIG. 4 is a schematic, transverse cross-sectional view of a tubularmembrane element used in a module of the present invention; and

FIG. 5 is a schematic, sectional view of a tubular membrane element usedin a module of the present invention.

DETAILED DESCRIPTION

With reference to FIG. 1, an electrically driven oxygen separator 1 ofthe present invention is illustrated that has two modules 10 housedwithin an enclosure 12. It is understood that there could be more orfewer modules 10 depending upon the application of an oxygen separationin accordance with the present invention.

With reference to FIG. 2, each of the module 10 are formed by a bundleof tubular membrane elements that are divided into a first portion ofthe tubular membrane elements 14 and a second portion of the tubularmembrane elements 16. The first and second portions of the tubularmembrane elements are held in position by end insulation members 18 and20 that are fabricated from high purity alumina fiber. The tubularmembrane elements for exemplary purposes can have an outer diameter ofabout 6.35 mm., a total wall thickness of about 0.5 mm. and a length ofabout 55 cm. The oxygen that is separated by such first and secondportions of the tubular membrane elements 14 and 16 are collected byfirst and second manifolds 22 and 24 that as illustrated are spacedapart from one another with the first and second portions of the tubularmembrane elements 14 and 16 located between the first and secondmanifolds 22 and 24.

The first and second manifolds 22 and 24 are connected to the first andsecond portions of the tubular membrane elements 14 and 16 such thatoxygen is received by the first manifold 22 from the first portion ofthe tubular membrane elements 14 and by the second manifold 24 from thesecond portion of the tubular membrane elements 16. With additionalreference to FIG. 3, the connection of the first manifold 22 isillustrated. Each of the first and second manifolds 22 and 24 areprovided with first elongated elements 26 and second elongated elements28 that radiate in a spider-like arrangement from a collection element30 that actually collects the oxygen that is separated by the first andsecond portions of the tubular membrane elements 14 and 16. Asillustrated, the first portion of the tubular membrane elements 14alternate with the second portion of the tubular membrane elements 16and the elongated elements 26 alternate with the elongated elements 28.The elongated elements penetrate the end seals 70 and 72 provided inopposite ends of both of the first and second portions of the tubularelements 14 and 16. The first elongated elements 26 are hollow tubes andthe second elongated elements 28 are of solid configuration, althoughsuch elongated elements 28 could be hollow tubes that are plugged. Inany case, since the first elongated elements 26 are hollow tubes, theoxygen will flow from the first portion of the tubular membrane elements14 to the collection element 30 while the oxygen will not flow from thesecond portion of the tubular membrane elements 16 to the collectionelements 30. At the opposite end of the module 10, however, the secondmanifold 24, that is identical to the first manifold 22, is slightlyrotated such that the first elongated elements 26 penetrate the endseals 72 of the second portion of the tubular membrane elements 16 andthe second elongated elements 28 penetrate the end seals 70 of the firstportion of the tubular membrane elements 16. As a result, the oxygenproduced by the second portion of the tubular membrane elements 16 iscollected by the collection element of the second manifold 24.Consequently, if one or more of the first portion of the tubularmembrane elements 14 fail, oxygen will still able to be produced, albeitat a lower flow rate, from the second portion of the tubular membraneelements 16 that have not failed and vice-versa.

As can be appreciated, it is possible to construct an embodiment of thepresent invention in which there is no such alternation of tubularmembrane elements and elongated elements. For example the first portionof the tubular membrane elements 14 could be located on one side and thesecond portion of the tubular membrane elements 16 could be located onthe other side of the module. In such case, the first elongated elements14 would be located one side of the module 10 and the second elongatedelements 16 would be located on the opposite side. Furthermore,embodiments of the present invention are also possible in which thetubular membrane elements are located in the same plane. As can beappreciated, the manifold in such case would have an elongatedcollection element with elongated elements extending therefrom at rightangles to penetrate the end seals of the tubular membrane elements. Inany embodiment, the tubular membrane elements are divided into portionssuch that one manifold will conduct the oxygen from one portion and theother manifold will conduct oxygen from the other portion.

With additional reference to FIG. 4, each of the tubular membraneelements 14 is provided with a cathode layer 34, an anode layer 36 andan electrolyte layer 38. Two current collector layers 40 and 42 arelocated adjacent the anode layer 36 and the cathode layer 34,respectively, to conduct an electrical current to the anode layer andthe cathode layer. Tubular membrane elements 16 are identical to tubularmembrane elements 14. Although the present invention has application toany composite structure making up a tubular membrane element 14, forexemplary purposes, the cathode layer 36 and the anode layer 34 can bebetween about 10 and about 50 microns thick and the electrolyte layer 38can be between about 10 microns and about 1 mm. thick, with a preferredthickness of about 500 microns. The electrolyte layer 38 is gasimpermeable and can be greater than about 95 percent dense andpreferably greater than 99 percent dense. Each of the cathode layer 36and the anode layer 34 can have a porosity of between about 30 percentand about 50 percent and can be formed from(La_(0.8)Sr_(0.2))_(0.98)MnO_(3-δ). The electrolyte layer 38 can be 6mol % scandium oxide, 1 mol % cerium oxide doped zirconium oxide. Thecurrent collector layers 40 and 42 can each be between about 50 andabout 150 microns thick, have a porosity of between about 30 percent andabout 50 percent and can be formed from a powder of silver particleshaving surface deposits of zirconium oxide. Such a powder can beproduced by methods well known in the art, for example by wash-coatingor mechanical alloying. For exemplary purposes, a silver powder,designated as FERRO S7000-02 powder, can be obtained from FerroCorporation, Electronic Material Systems, 3900 South Clinton Avenue,South Plainfield, N.J. 07080 USA. The size of particles contained insuch powder is between about 3 and about 10 microns in diameter and theparticles have a low specific surface are of about 0.2 m²/gram. Zirconiasurface deposits can be formed on such powder such that the zirconiaaccounts for about 0.25 percent of the weight of the coated particle.

During operation of the oxygen separator 1, the oxygen contained inoxygen containing feed stream 44 contacts the current collector layer 40and permeates through pores thereof to the cathode layer 36 which asindicated above is also porous. The oxygen ionizes as a result of anelectrical potential applied to the cathode and anode layers 34 and 36at current collector layers 40 and 42. The resulting oxygen ions aretransported through the electrolyte layer 38 under the driving force ofapplied potential and emerge at the side of the electrolyte layer 38adjacent the anode layer 34 where electrons are gained to form elementaloxygen. The oxygen permeates through the pores of the anode layer 36 andthe adjacent current collector 42 where the oxygen passes into theinterior of the tubular membrane elements 14. The same function, in thesame manner would be obtained for tubular membrane elements 16.

It is to be noted, that although the cathode layer is located on theoutside of the tubular membrane elements 14 and 16, it is possible toreverse the layers so that the anode layer were located on the outsideof the tubular membrane elements 14 and 16 and the cathode layer werelocated on the inside. Such an embodiment would be used where the devicewere used as a purifier. In such case the oxygen containing feed wouldflow on the inside of the tubular membrane elements 14.

With continued reference to FIG. 5, it can be seen that the outer,opposite end sections of each of the tubular membrane elements 14 arelocated within end insulation members 18 and 20. It is to be noted thatthe following discussion would have equal applicability to tubularmembrane elements 16. As a result, there is essentially no oxygentransport taking place at such locations. As illustrated, the ends ofeach of the tubular membrane elements 14 are devoid of both the cathodelayer 36 and its associated current collector 40 and the anode layer 34and its associated current collector 42 so that current does not flowwithin the tubular membrane elements 14 at such locations. It has beenfound that where the tubular membrane elements are designed withelectrical current flow within such insulated end section, the ceramicwill tend to undergo a chemical reduction reaction at such end sectionswith a consequent potential of a failure of the elements. It is to benoted that embodiments of the present invention are possible in whichthe anode and cathode layers and their associated current collectorlayers extend to the physical ends of the tubular membrane elements 14even when covered with an end insulation members.

Tubular membrane elements 14 and 16 incorporate end seals 70 and 72formed at the opposite ends thereof. Each of the end seals 70 and 72 areformed by plug-like members 74 and 76 that are each fabricated from anelastomer to effect a hermetic seal at the ends of the tubular membraneelements 14 and 16. A suitable elastomer is a VITON® fluoroelastomerobtained through Dupont Performance Elastomers of Willmington, Del.,United States of America.

During operation of tubular membrane elements 14 and 16 oxygen willaccumulate and will tend to force the plug-like members 74 and 76 in anoutward direction and from the ends of tubular membrane elements 14 and16. In order to retain the plug-like members 74 and 76 within the end oftubular membrane elements 14 and 16, deposits of a ceramic adhesive 78and 80 are introduced into the ends of tubular membrane elements 14 and16 at a location adjacent to plug-like member 74 and plug-like member76, respectively. A suitable ceramic adhesive can be a RESBOND™ 940 fastsetting adhesive manufactured by Cotronics Corporation of Brooklyn,N.Y., United States of America. It is to be noted that other suitablemeans to retain plug-like member 74 and 76 could be employed such asmechanical keys located adjacent to plug-like member 74 that penetrateopposed transverse bores defined at the ends of tubular membraneelements 14 and 16 or sleeves cemented in place within the ends oftubular membrane elements 14 and 16.

As illustrated, an elongated element 28 penetrates the deposit 78 andthe plug-like member 74 along with an electrical feed through 82 and anelongated elements 26 penetrates deposit 80 and plug-like member 76. Inthis regard an axial bore 84 and 86 are defined within plug-like member74 for penetration of electrical feed through 82 and the secondelongated element 28. An axial bore 88 is provided within plug-likemember 76 for penetration of the elongated element 26.

In order to install plug-like members 74 and 76 within the end oftubular membrane elements 14 and 16, the same is fabricated with alarger outer diameter than the inner diameter of tubular membraneelements 14 and 16 and then cooled with liquid nitrogen. The percentagedifference in diameters can be about 10 percent. Thereafter, plug-likemembers 74 and 76 are installed in the ends of tubular membrane elements14 and 16 and as such members warm to ambient temperature, the sameexpands to produce a hermetic seal within the ends of tubular membraneelement 14 and 16. Additionally, each of the bores 84, 86 and 88 are allsized smaller than the associated electrical feed through 82 and theelongated elements 28 and 26. After installation and warming of theplug-like members 74 and 76, the electrical feed through 84 and theelongated elements 28 and 26 are forced through the smaller bores tocreate hermetic seals. Thereafter, the ends are filled with the depositsof ceramic adhesive 78 and 80 to complete the end seals. As could beappreciated, other types of end seals are known in the art such asceramic end caps and ceramic deposits within the tubes.

The potential is applied to each of the tubular membrane elements 14 and16 by means of a connection to the current collector layer 42 adjacentof the cathode layer 34 by means of a conductor 90 that is looped aroundthe current collector layer 42 by a loop 92 that is held in place bysilver paste 94. Connection is established to current collector layer 40adjacent the anode layer 36 by means of a conductor 90 that is attachedto a current distributor 98 of helical configuration. Conductor 90passes through the electrical feed through 82.

Although the tubular membrane elements 14 and 16 could be connected inparallel, preferably a series connection is established in which thecurrent collector 40 of each of the tubular membrane elements 14 and 16is connected to the current collector 42 of the next in series of thetubular membrane elements 14 and 16. Therefore, the current collector 40of each particular first tubular membrane element 14 is connected to thecurrent collector 42 of the second tubular membrane element 16 locateddirectly adjacent thereto and the current collector 42 of the secondtubular membrane element 16 is connected to the current collectorelements 40 of the next, adjacent first tubular membrane element. Thus,as can best be seen in FIG. 3, the conductor 90 of each of the firsttubular membrane elements 14 is connected to the end of the electricalfeed through 82 of each of the adjacent second tubular membrane elements16 and the conductor 90 passes through the second insulating member 20for connection to such adjacent first tubular element 14 at loop 92thereof Since the first tubular membrane elements 16 and the secondtubular membrane element 14 are reversed, at the first insulating member18, the conductor 90 connects to the electrical feed through 82 of eachof the first tubular membrane elements 14, passes through the firstinsulating member 18 and then is connected to the second tubularmembrane elements 16 via the loop 92 thereof This being said in case oftwo adjacent first and second tubular membrane elements 14 and 16, suchconnection between the elements as aforesaid is not established andinstead, power cords 100 and 102 are connected to the electrical feedthrough 82 of the second tubular membrane element 16 and the currentcollector layer 42 of the first tubular membrane element 14 so that theelectrical potential can be applied to the first and second tubularmembrane elements 14 and 16.

With reference again to FIG. 1, the enclosure 12 has two opposite endwalls 104 and 106 provided within opposite openings 108 and 110 withinwhich the insulating members 18 and 20 are lodged with the ends of thefirst and second tubular membrane elements 14 and 16 exposed. Theopposite end walls 104 and 106 are connected by a sidewall 112 therebydefine a heated enclosure 114 that is heated by heating elements 116embedded within the sidewall 112. Attached to the end walls 104 and 106are inlet regions 120 and 122 defined by the interior of cowlings 124and 126, respectively. Attached to the cowlings 124 and 126 are blowers128 and 130, respectively, that direct feed air streams 44 and 44 to theinlet regions 120 and 122. With brief reference to FIG. 3, theinsulating member 20 is provided with an opening in the form of an axialbore 136 that allows part of the feed air stream 44 to flow past theends of the tubular membrane elements 14, 16 and thereby cool the endsand the deposits of elastomer that form the end seals before passinginto the heated enclosure 114 and contact the first and second tubularmembrane elements 14 and 16. Although not illustrated, insulating member18 is provided with a like opening to allow at least a portion of thefeed air stream 44 to flow past the exposed ends of the first and secondtubular membrane elements 14 and 16 and into the heated enclosure 114for the same purpose. The separation of the oxygen from the feed airstreams 44 and 44 form a retentate that is discharged from the heatedenclosure 114, through an exhaust 136 as a retentate stream 138.

As can be appreciated, embodiments of the present invention are possiblein which in place of the axial bores or other openings within insulatingmembers 18 and 20, openings could be situated within the end walls 104and 106. The ends of the first and second tubular membrane elements 14and 16 would not be cooled to the same extent as in the illustratedembodiment. Also, the openings in the insulating members, such as theillustrated insulating members 18 and 20 could be used in connectionwith an embodiment that did not have the first and second manifolds 22and 24 of the present invention; or in other words, a single manifoldcollecting oxygen from all tubular membrane elements used in suchembodiment.

With reference again to FIG. 2, oxygen product streams 140 and 142 arewithdrawn from the first tubular elements 14 and the second tubularelements 16 by lines 144 and 146 connected to the collection elements 30of second and first manifolds 24 and 22, respectively. Although notillustrated, the lines would pass through the cowlings 124 and 126 andthen to a collection tank that would collect the oxygen product atpressure. As mentioned above, a central advantage of having the separateportions of the tubular membrane elements 14 and 16 is to preventfailure of the oxygen separation device 1 upon failure of a tubularmembrane element. Moreover, where oxygen separation device 1 is used tosupply oxygen to a tank under pressure, if a tubular membrane elementfailed, then product would be lost from the tank. In order to preventthis, check valves 148 and 150 are provided to isolate the first tubularmembrane elements 14 from the second tubular membrane elements 16,respectively, and thereby to prevent the loss of pressurized productoxygen upon failure of a tubular membrane element of either of the twoportions.

Although the present invention has been described with reference to apreferred embodiment, as will occur to those skilled in the art,numerous changes, additions and omission may be made without departingfrom the spirit and scope of the present invention as set forth in theappended claims.

1-15. (canceled)
 16. An oxygen separator module for an electricallydriven oxygen separator apparatus, said oxygen separator modulecomprising: a plurality of tubular membrane elements pneumaticallycoupled together, each of the tubular membrane elements having an anodelayer, a cathode layer, an electrolyte layer located between the anodelayer and the cathode layer and each of the tubular membrane elementsconfigured to separate oxygen from an oxygen containing feed stream whenan electric potential difference is applied between the anode layer andthe cathode layer to induce oxygen ion transport in the electrolyte; aplurality of end seals located at opposite ends of the plurality oftubular membrane elements; end insulation members located proximate theend seals wherein the plurality of tubular membrane elements arearranged in a bundle and held in place by the end insulation members; aplurality of hollow tubes penetrating one or more of the end seals atopposite ends of the plurality of tubular membrane elements, the hollowtubes configured to permit flow of oxygen from the interior of thetubular membrane elements; the at least one oxygen separation modulefurther having one or more openings or inlets located within the endinsulation members to allow passage of the oxygen containing feed streamthrough the end insulation members and across exterior surfaces of theplurality of tubular membrane elements between the end insulationmembers; and at least one manifold configured to collect the oxygen fromthe plurality of tubular membrane elements, the at least one manifoldconnected to the plurality of tubular membrane elements such that oxygenis received by the at least one manifold from some or all of theplurality of tubular membrane elements via one or more of the pluralityof hollow tubes.
 17. (canceled)
 18. (canceled)
 19. The module of claim16, wherein the end seals further comprise: plug-like members locatedwithin the tubular membrane elements and formed by an elastomer toproduce hermetic seals at the opposite ends of the plurality of tubularmembrane elements; and deposits of a ceramic adhesive located within theplurality of tubular membrane elements adjacent to the plug-like membersand positioned to prevent outward movement of the plug-like members. 20.(canceled)
 21. The module of claim 16, wherein each of the plurality oftubular membrane elements has an inner anode layer, an outer cathodelayer, an electrolyte layer located between the anode layer and thecathode layer to form the electrolyte and two current collector layerslocated adjacent to and in contact with the anode layer and the cathodelayer and situated on the inside and outside of the tubular membraneelements to allow the electrical potential to be applied by a powersource.
 22. The module of claim 21, wherein the plurality of tubularmembrane elements are electrically connected in series and the tubularmembrane elements contain current distributors of helical configurationin contact with one of the two current collector layers on the inside ofthe tubular membrane elements to conduct an electrical current fromelectrical conductors passing through the end seals via feed throughs.23-28. (canceled)
 29. A plurality of oxygen separator modules as setforth in claim 16 wherein each oxygen separator module further comprisesat least one check valve disposed between the at least one manifold andthe plurality of tubular membrane elements or between the at least onemanifold and a tank, the check valves configured to pneumaticallyisolate the oxygen separator module from one another upon failure of oneof the oxygen separator modules or to pneumatically isolate one or moretubular membrane elements in each oxygen separator module upon failureof one or more tubular membrane elements.
 30. The module of claim 16wherein the at least one manifold further comprises a first manifold anda second manifold spaced apart from one another with the tubularmembrane elements situated therebetween and configured to receive oxygenfrom the tubular membrane elements such that oxygen is received by thefirst manifold from a first group or portion of the tubular membraneelements and oxygen is received by the second manifold from a secondgroup or portion of the tubular membrane elements wherein, upon failureof at least one of the tubular membrane elements in either the firstgroup or portion or the second group or portion of the tubular membraneelements, oxygen is able to be collected from either the first group orportion or the second group or portion of the tubular membrane elementsthat do not include the at least one of the tubular membrane elementsthat has failed.